Aphelios is a Hyperscaling lategame carry with insane Dmg potential if played well.
He scales with Player skill. He is High Risk High Reward Playstyle if u do one mistake u die basically everytime unless ur fed.

Your Early isnt special to other Hypercarries but lvl 1 - 3 u have good Range with Calibrum (650) which is good for poke in lane. You can all in with the right weapons early game.
You can use Red Q into Green auto in lane for a bit of poke when Red is gone it gets better. Green Purple is the best early game combo u can Green Q Auto then Purple Q for root and ur support can engage with the free long range root.
But mostly u want to chill early and get ur spikes asap.

Your Mid Game is pretty decent with 2 items you wins basically every 1v1 if u have red white or green white and ur teamfights are fine as well with Blue Purple.
Biggest focus is still Farming and getting to 3 Items.

You have done it u scaled to 3 Items now ur champ is insanely strong in every situation. Blue Purple for Teamfights, Red White Greenfor small skirmishes and 1v1 / 1v2. Your dmg now is disgusting u just need to survive and get your dmg out as good as possible.

Aphelios has a lot of Combos due to his 5 weapons there are 2 Gun Orders you can use.

You always start with Red -> Green -> Purple -> Blue -> White
Your Ideal cycle is Red -> White -> Green -> Purple -> Blue
You can also do Red -> White -> Green -> Blue -> Purple bit more dmg but less utility

For the 1. Cycle you want to get rid of Red first and then you always get rid of the Gun u had before u got the next one.

Red Green
Green Purple
Purple Blue
Blue White
Red White
White Green
Green Purple
Purple Blue

For the 2nd Cycle you get rid of Red first aswell but u dont always get rif of the weapon u had first only if you have Purple Blue you get rid of Blue first instead of Purple. After that you do the same you get rid of the weapon u had first.

Red Green
Green Purple
Purple Blue
Purple White
Red White
White Green
Green Blue
Blue Purple
Purple Red

Those are the 2 viable Cycles u should follow.